It's unclear what your configuration is but if you have a group of PC's and the files you want to cast are on shared network resources, that is you can open the file on the pc your on and you use chrome with the google google cast and videostream extensions then yes, it will work. Any device such as a ASUS router that supports Samba or another PC with network shares with the proper share setup should work, I do it everyday. You should not need the internet to do this, as long as you can open the remote files on the local PC.

In Chrome add the 'Google Cast' extension to connect to Chromecast and the 'Videostream for Google Chromecast' extension to play videos via Google cast. There are other Extensions in chrome that I haven't really played with.